Elastoacoustic wave propagation in a biphasic mechanical metamateriala)

Meng Wang; Annamaria Pau; Marco Lepidi

doi:10.1121/10.0026079

Elastoacoustic wave propagation in a biphasic mechanical metamateriala)

J Acoust Soc Am. 2024 May 1;155(5):3322-3335. doi: 10.1121/10.0026079.

Authors

Meng Wang¹, Annamaria Pau², Marco Lepidi³

Affiliations

¹ Department of Astronautical, Electrical and Energy Engineering, Sapienza University of Rome, Rome, Italy.
² Department of Structural and Geotechnical Engineering, Sapienza University of Rome, Rome, Italy.
³ Department of Civil, Chemical and Environmental Engineering, University of Genoa, Genoa, Italy.

PMID: 38758055
DOI: 10.1121/10.0026079

Abstract

Humans are sensitive to air-borne sound as well as to mechanical vibrations propagating in solids in the frequency range below 20 kHz. Therefore, the development of multifunctional filters for both vibration reduction and sound insulation within the frequency range of human sensitivity is a research topic of primary interest. In this paper, a high-contrast biphasic mechanical metamaterial, composed of periodic elastic solid cells with air-filled voids, is presented. By opening intercellular air-communicating channels and introducing channel-bridging solid-solid couplings, the frequency dispersion spectrum of the metamaterial can be modified to achieve complete and large bandgaps for acoustic and elastic waves. From a methodological viewpoint, the eigenproblem governing the free wave propagation is solved using a hybrid analytical-computational technique, while the waveform classification is based on polarization factors expressing the fraction of kinetic and elastic energies stored in the solid and fluid phases. Based on these theoretical results, a mechanical metafilter consisting of an array of a finite number of metamaterial cells is conceived to provide a technical solution for engineering applications. The forced response of the metafilter is virtually tested in a computational framework to assess its performance in passively controlling the propagation of broadband sound and vibration signals within solid and fluid environments. Quantitative results synthesized by transmission coefficients demonstrate that the metafilter can remarkably reduce the transmitted response in the frequency band of human sensitivity.